MongoDB · Reference & Practice

Mongo
DB

44 reference files covering every core topic — from CRUD basics to sharding, change streams, and production best practices. Plus a comprehensive Q&A drill sheet.

44Topic Files

308Sections

24Q&A Categories

200+Practice Questions

Practice Questions & Answers

24 sections · 200+ questions · Basic → Advanced · Interactive answer toggles · Progress tracking

Foundations 3 files

What is MongoDB · Document model · vs relational · Use cases · Atlas setup

Databases & Collections

create · drop · list · stats · capped collections · naming rules

Documents & BSON

BSON types · ObjectId · Date · Decimal128 · Binary · field limits

CRUD Operations 4 files

insertOne · insertMany · ordered · _id generation · write concern

find · findOne · filters · projection · cursor methods

updateOne · updateMany · replaceOne · upsert · findOneAndUpdate

deleteOne · deleteMany · findOneAndDelete · drop · TTL

Query Operators 4 files

Query Operators

$eq $ne $gt $gte $lt $lte $in $nin · comparison operators

Logical Operators

$and $or $not $nor · combining conditions · implicit $and

Element Operators

$exists · $type · BSON type codes · null vs missing

Array Operators

$all $elemMatch $size · querying arrays · nested documents

Update Operators 2 files

Update Operators

$set $unset $inc $mul $rename $min $max $currentDate · field-level

Array Update Operators

$push $pop $pull $addToSet $each $sort $slice $position · positional $

Query Modifiers 3 files

include/exclude fields · $slice · $elemMatch · $meta · covered queries

Sorting, Limiting & Skipping

sort() · limit() · skip() · multi-field sort · natural order · pagination

next() · hasNext() · forEach() · toArray() · batchSize · cursor lifecycle

Aggregation 6 files

Aggregation Intro

pipeline concept · aggregate() · allowDiskUse · explain · vs MapReduce

Aggregation Stages

$match $project $sort $limit $skip $count $set $unset $out $merge

Aggregation Expressions

$add $subtract $multiply $divide · $concat $toLower · $cond $switch · $$vars

Aggregation $lookup

left outer join · pipeline $lookup · let · multiple joins · performance

Aggregation $unwind

deconstruct arrays · includeArrayIndex · preserveNullAndEmpty · regroup

Aggregation $group

$sum $avg $min $max $first $last $push $addToSet · _id grouping key

Indexes 5 files

B-tree structure · createIndex · listIndexes · dropIndex · write overhead

single-field · compound · multikey · text · 2dsphere · wildcard · hashed

Compound Indexes

ESR rule · prefix queries · sort direction · index intersection · coverage

Index Properties

unique · sparse · partial · TTL · hidden · collation · background build

queryPlanner · executionStats · allPlansExecution · IXSCAN vs COLLSCAN · nReturned

Schema Design 4 files

access patterns · embed vs reference · document size · 16MB limit · $jsonSchema

Embedding vs Referencing

one-to-one · one-to-many · many-to-many · denormalization tradeoffs

Data Modeling Patterns

Bucket · Outlier · Computed · Polymorphic · Subset · Extended Reference

DBRef · manual references · $graphLookup · tree structures · adjacency list

Transactions 1 file

multi-document ACID · session · startTransaction · commitTransaction · TransientTransactionError retry

Infrastructure 6 files

replica set · oplog · elections · read preference · write concern · failover

shard key · hashed vs ranged · chunks · mongos · balancer · zone sharding

Security & Auth

authentication · SCRAM · x.509 · TLS · LDAP · network binding · authSource

Roles & Privileges

built-in roles · custom roles · grantRolesToUser · least privilege · createUser

Backup & Restore

mongodump · mongorestore · Atlas backup · oplog replay · point-in-time · PITR

Monitoring & Profiling

serverStatus · currentOp · db.profiler · system.profile · $indexStats · Atlas metrics

Specialized Features 4 files

GeoJSON · 2dsphere index · $near $geoWithin $geoIntersects · $nearSphere

text index · $text $search · $meta textScore · language · phrases · negation

watch() · event types · resume tokens · pipeline filtering · fullDocument · pre-image

timeseries collection · timeField granularity · $setWindowFields · $densify · partitioning

Production 2 files

error codes · WriteError · BulkWrite · connection errors · timeouts · retry patterns

connection singleton · schema rules · indexing · query patterns · security checklist · production checklist